In recent years, it has become desirable to increase the thermal conductivity of packaging materials in semiconductor devices for power control of hybrid vehicles, electric vehicles and the like and CPUs for high speed computers so that the temperature of internal semiconductors does not excessively increase. That is, an ability to effectively dissipate heat generated by semiconductor chips to the outside is important. In addition, thermal distortion may occur due to a difference between thermal expansion coefficients of materials used in a package according to an increase in the operating temperature, which results in a problem of a lifespan being reduced due to detachment of wires and the like.
As a method of solving such a heat dissipation problem, a heat dissipation method in which a material having high thermal conductivity (a heat dissipating member) is brought in contact with a heat generating portion to conduct heat to the outside may be exemplified. Examples of a material having high thermal conductivity include inorganic materials such as metals and metal oxides. In particular, use of aluminum nitride is preferred because it has a similar thermal expansion coefficient to that of silicon. However, such inorganic materials have problems of processability and crackability and it is difficult for such inorganic materials to have satisfactory characteristics as substrate materials in a package. Therefore, the development of a heat dissipating member having high thermal conductivity obtained by combining such an inorganic material and a resin has been conducted.
In order to increase the thermal conductivity of a resin composite material, in general, a large amount of a metal filler or an inorganic filler has been added to a commodity resin such as a silicone resin, a polyamide resin, a polystyrene resin, an acryl resin, and an epoxy resin. However, the thermal conductivity of the inorganic filler is a value specific to a substance and an upper limit thereof is fixed. Therefore, there have been many attempts regarding methods of improving thermal conductivity of a resin and thermal conductivity of a composite material from the bottom up.
In Patent Literature 1, as a method of improving thermal conductivity of a resin, a heat dissipating member obtained by performing orientation control on a liquid crystal composition using an orientation control additive and a rubbing treatment method and performing polymerization is disclosed.